Project ID: 2009RI82B
Title: Sequential Inactivation of Microorganisms in Drinking Water using Ultraviolet Radiation and Residual Chlorine
Project Type: Research
Start Date: 4/01/2009End Date: 3/31/2010
Congressional District: 1st
Focus Categories: Water Supply, Water Use
Keywords: Disinfection, Ultraviolet Radiation, Chlorine, Sequential Inactivation
Principal Investigator: Pennell, Kelly G.
Federal Funds: $ 15,263Non-Federal Matching Funds: $ 30,537Abstract: Water disinfection is commonly practiced throughout the United States to prevent disease outbreak from consumption of microbial-contaminated drinking water. The most common disinfection technique applied is chlorine. Concern over chlorination has been rising over the past several years due to the formation of disinfection byproducts, which include chloroform, other trihalomethanes (THMs), and haloacetic acids (HAAs), as well as Cryptosporidium parvum's reported resistance to chlorine-based disinfectants.

As an alternative to chlorine disinfection, some water and wastewater treatment systems are incorporating ultraviolet (UV) radiation. UV radiation is a broad spectrum antimicrobial agent that has limited potential for DBP formation. Over 400 UV disinfection facilities exist worldwide, including several large UV installations being constructed and/or designed for municipalities such as Seattle, WA (180-mgd) and New York City (2,200 mgd). One reason for interest in UV radiation for water disinfection is its effectiveness at inactivating Crypotosporidum, which has recently been targeted in water treatment regulations. Despite the promise of UV radiation as a disinfectant, there are some concerns over its use, for instance, it does not provide a residual disinfectant.

Sequential disinfection processes use two or more disinfectants with fundamentally different mechanisms of inactivation and have the potential to target a wider range of microorganisms than either disinfectant alone. They are often considered when the primary disinfectant is not capable of providing a long-lasting residual (such as the case with UV radiation, ozone, etc.), or when a synergistic response is developed through the combined application of disinfectants. Sequential disinfection may also be employed as a means of broadening antimicrobial behavior in a treatment setting, relative to the application of a single disinfectant.

The proposed research will focus on evaluating the effectiveness of UV radiation followed by chlorination. This application is appropriate for not only large water treatment systems that may have long distribution times, thereby requiring a residual disinfectant, but also for smaller scale systems where UV treatment can be practiced on a routine basis and augmented with residual chlorine, as needed. Better understanding of disinfection systems, especially those that have potential to target a broader microorganism population, while being inherently less susceptible for DBP formation due to a decrease in chemical use, is beneficial to virtually any water supply system.

The proposed research has the following research objectives:

To evaluate whether exposure to UV and chlorine results in enhanced inactivation, as compared to either disinfectant alone.

To determine whether spore inactivation via UV followed by chlorine is influenced by the UV dose-response behavior of the microorganism.

To form a hypothesis for why sequential disinfection using UV and chlorine is or is not influenced by the dose-response behavior of the microorganism to each disinfectant.

To investigate whether tailing of the dose-response curves can be lessened through the sequential application of UV and chlorine.